Efficient drying and pyrolysis of carbon-containing material

Abstract

A method and apparatus for drying and pyrolyzing carbon-containing materials to produce valuable products including char, oil, gas and thermal energy. The present invention involves a method whereby carbon-containing material 1 is maintained in a heated region predominantly free of oxidizing gases to promote pyrolysis reactions, and the thermal energy required to drive the process is provided via the combustion of a proportion of the volatilized matter with an oxygen containing gas in the same chamber 3 . The arrangement of the chamber 3 eliminates the need for any form of solid physical barrier between the concurrent pyrolysis and combustion reactions occurring in the process, and also avoids any requirement for external means of recirculating the gaseous volatilized matter. The present invention also relates to a method for improving the transfer of thermal energy from the combustion to pyrolysis zones via radiative and convective heat transfer mechanisms.

The invention claimed is: 
     
       1. An apparatus for drying and pyrolyzing a carbon-containing feedstock, the apparatus comprising:
 a reaction chamber that is substantially sealed, the reaction chamber for locating therein the carbon-containing feedstock, the reaction chamber comprising:
 one or more inlet ports in an upper portion of the reaction chamber, the inlet ports connected to an oxygen-containing gas source to control a flow rate of an oxygen-containing gas to the reaction chamber; and 
 one or more outlet ports in a lower portion of the reaction chamber positioned so that gases, generated within the reaction chamber, flow downwards through the carbon-containing feedstock and escape out through the one or more outlet ports; and 
 temperature probes configured to provide temperature measurements in the upper portion and the lower portion of the reaction chamber; 
 
 wherein, in use, the carbon-containing feedstock is positioned in the reaction chamber such that a top portion of the carbon-containing feedstock is above the one or more outlet ports and at or below the one or more inlet ports; 
 a control system operably connected with the temperature probes and the oxygen-containing gas source to further control the flow rate of the oxygen-containing gas so that combustion of the top portion of the carbon-containing feedstock in an initial combustion phase provides initial heat to raise a temperature of the carbon-containing feedstock so that pyrolysis commences; 
 wherein the control system also further controls the flow rate of the oxygen-containing gas in response to the temperature measurements so that the temperature measurement in the upper portion of the reaction chamber does not exceed a maximum of 500° C. to 1000° C., and the temperature measurement in the lower portion of the reaction chamber achieves a minimum target temperature of 150° C. to 600° C., so as to establish a zone or region of volatile gas combustion in the upper portion of the reaction chamber above the top portion of the carbon-containing feedstock thereby driving further pyrolysis of the carbon-containing feedstock, generating a net flow of non-oxidizing hot combustion products gases downwards through the carbon-containing feedstock and out through the one or more outlet ports thereby heating the carbon-containing feedstock and driving further pyrolysis; 
 wherein the control system also further controls the flow rate of the oxygen-containing gas so that the zone or region of volatile gas combustion provides complete consumption of free oxygen in the oxygen-containing gas thereby preventing free oxygen from contacting the carbon-containing feedstock; and 
 a perforated-cage arrangement to be loaded with the carbon-containing feedstock and then inserted into the reaction chamber. 
 
     
     
       2. The apparatus of  claim 1 , wherein the reaction chamber further comprises a re-sealable hatch door openable for inserting the perforated-cage arrangement loaded with the carbon-containing feedstock into the reaction chamber. 
     
     
       3. The apparatus of  claim 1 , wherein at least one inlet port in the one or more inlet ports comprises a baffle or diffuser positioned to assist in distributing the oxygen-containing gas entering the reaction chamber. 
     
     
       4. The apparatus of  claim 1 , further comprising one or more water sprayers in the upper portion of the reaction chamber. 
     
     
       5. The apparatus of  claim 1 , wherein the reaction chamber further comprises a pressure relief device configured to release excess pressure in the reaction chamber. 
     
     
       6. A method of drying and pyrolyzing carbon containing feedstock in a reaction chamber that is substantially sealed, the reaction chamber comprising one or more inlet ports in an upper portion thereof, and one or more outlet ports in a lower portion thereof, the one or more inlet ports connected to an oxygen-containing gas source, the oxygen-containing gas source configured to supply an oxygen-containing gas to the reaction chamber, the one or more outlet ports positioned to exhaust gases generated within the reaction chamber after percolating downwards through a carbon-containing feedstock, the method including the steps of:
 loading a perforated-cage arrangement with the carbon-containing feedstock and then inserting the perforated-cage arrangement into the reaction chamber such that, a top portion of the carbon-containing feedstock is above the at least one of the one or more outlet ports and at or below at least one of the one or more inlet ports, 
 operably connecting temperature probes with a control system to provide temperature measurements in the upper portion and the lower portion of the reaction chamber; 
 operating the control system to combust the top portion of the feedstock to provide heat for drying and pyrolyzing the carbon-containing feedstock in the reaction chamber, and 
 operating the control system to control:
 a flow of the oxygen-containing gas in response to a temperature measurement in the upper portion of the reaction chamber and a temperature measurement in the lower portion of the reaction chamber, so that the temperature measurement in the upper portion of the reaction chamber does not exceed a maximum of 500 to 1000° C., and the temperature measurement in the lower portion of the reaction chamber achieves a minimum target temperature of 150° C. to 600° C., so as to establish a zone or region of volatile gas combustion in the upper portion of the reaction chamber above the top portion of the feedstock thereby driving further pyrolysis of the feedstock, generating a net flow of non-oxidizing hot combustion products gases downwards through the carbon-containing feedstock and out through the one or more outlet ports thereby heating the carbon-containing feedstock and driving further pyrolysis; and 
 maintaining a flow rate of the oxygen-containing gas so that the zone or region of volatile gas combustion provides complete consumption of free oxygen in the oxygen-containing gas thereby preventing free oxygen from contacting the carbon-containing feedstock. 
 
 
     
     
       7. The method of  claim 6 , further comprising the step of providing one or more ignition sources configured to ignite the top portion of the carbon-containing feedstock. 
     
     
       8. The method of  claim 7 , further comprising the step of reducing flow of oxygen-containing gas into the reaction chamber when at least one of the temperature measurements in the lower portion of the reaction chamber reaches the minimum target temperature. 
     
     
       9. The method of  claim 6 , further comprising the step of maintaining the minimum target temperature for a specified time period. 
     
     
       10. The method of  claim 9 , further comprising the step of stopping flow of oxygen-containing gas into the reaction chamber once the specified time period has elapsed. 
     
     
       11. The method of  claim 6 , further comprising the step of pre-heating the oxygen-containing gas using an external heat source acting on the oxygen-containing gas prior to the oxygen-containing gas entering the reaction chamber. 
     
     
       12. The method of  claim 6 , further comprising the step of preheating the oxygen-containing gas prior to the oxygen-containing gas entering the reaction chamber using heat recovered from the gases exhausted from the reaction chamber via the one or more outlet ports.